Vibrator and vibratory system

ABSTRACT

A vibrator comprises a vibratory unit composed of resilient sheet material and having two main vibratory arms disposed in spaced parallel relationship and interconnected at their ends by two connecting end portions. A pair of central vibratory arms extend inwardly from each connecting end portion in a direction towards each other and the central arms and the main arms all lie in a common plane. The vibratory system comprises the vibrator in combination with a driving magnet connected to one of the central arms thereof and a driving coil coacting with the driving magnet to alternately drive same to effect flexural vibration of the central arm accompanied by vibration of the main vibratory arms. A driven magnet is connected to either the same central arm or the other central arm of the vibrator and coacts with a magnetic follower wheel to rotationally drive the follower wheel in an intermittent manner in accordance with the vibratory motion of the main vibratory arms.

D United States Patent [in [H] 3,864,586

Saito l l Feb. 4, 1975 VIBRATOR AND VIBRATORY SYSTEM PrimaryExaminer-Donovan F. Duggan Attorney, Agent, or Firm-Robert E Burns; [75]Inventor. lliroshl SaIto, Omiya, Japan Emmanual J- Labam; Bruce L Adams[73] Assignee: Kabushiki Kaisha Seikosha, Tokyo,

Japan {57] ABSTRACT [22] Filed: Sept. 13, I973 A vibrator comprises avibratory unit composed of re silient sheet material and having two mainvibrator [2]] Appl' 396675 arms disposed in spaced parallel relationshipand in terconnected at their ends by two connecting end por- [30]Foreign Application Priority Data tions. A pair of central vibratoryarms extend inwardly seph 14 972 Japan H 471M301 from each connectingend portion in a direction to- Oct 20, 1972 Japan H 47405064 wards eachother and the central arms and the main arms all lie in a common plane.The vibratory system 52 us. Cl 310/21, 310/22, 310/25, comprises thevibrator in Combination with a driving 58/23 v 58/23 D magnet connectedto one of the central arms thereof 51 Int. Cl. H02k 7/06 and a drivingcoming with the driving magnet to 5 pick f Search 310/21 25 58/23 R,alternately drive same to effect flexural vibration of 53 23 TF 23 v 2334 409 457; 331 15 the central arm accompanied by vibration of the mainvibratory arms. A driven magnet is connected to ei- 5 References Citedther the same central arm or the other central arm of UNITED STATESPATENTS the vibrator and coacts with a magnetic follower wheel torotationally drive the follower wheel in an ina il termittent manner inaccordance with the vibratory 314913257 1/1970 ogie''fffIIIIIIIIIIIIIIIIIIIIIIIII 310/25 X move of the main vibratory 9Claims, 12 Drawing Figures PATENTED 3.864.586

SHEH 20F 4 PATENTED H975 3.864.586

sum 30? 4 1 VIBRATOR AND VIBRATORY SYSTEM The present invention relatesgenerally to mechanical vibrators and more particularly, to a mechanicalvibrator especially designed for use in a timepiece or as a mechanicalfilter.

Various types of mechanical vibrators are known in the art and of thevarious types, the tuning fork vibrator has proven to be especiallysuitable and reliable for use in timepieces. One type of tuning forkwhich is widely used in the art has three tines or prongs and has adriving magnet secured to the free end of the central tine and a set ofweighting or balancing masses affixed to the free ends of the other twotines. The central tine moves through an arc of a circle during use ofthe vibrator and consequently, sufficient clearance must be providedbetween the path of travel of the driving magnet and the interior of thedriving coil.

Since the driving magnet undergoes pivotal movement into and out of theinterior ofthe driving coil, sufficient clearance space must be leftbetween the innermost turns of the coil and the angular path of travelof the driving magnet so as to preclude collision between the two andsuch an arrangement results in a low driving efficiency of the vibratordue to the comparatively wide air space. Furthermore, such a tuning forkvibrator is of the cantilever type wherein all the vibratory arms aresecured at one end to a support and are free at their other ends andthis type of vibrator readily undergoes vibrational mode changes and issusceptible to vibrating in spurious vibrational modes rather than theintended normal vibrational mode.

The present invention eliminates the aforementioned disadvantages of theconventional tuning fork vibrator. The vibrator of the invention iscomposed of resilient sheet material and has two main vibratory armswhich are interconnected at their ends by respective connecting endportions and the vibrator has two central vibratory arms which eachproject inwardly from one of the connecting end portions towards eachother and terminate in spaced opposed relationship from each other. Adriving magnet is secured to one of the central arms and is magneticallydriven during use of the vibrator to vibrate the central arm andaccordingly vibrate the two main vibratory arms in a predeterminednormal vibrational mode.

During operation of the vibrator, the free end of the driven central armpivots about the corresponding connecting end portion of the vibratorand once the main vibratory arms begin to vibrate, they in turn pivotabout a pivot located at the other connecting end portion and as aresult of the different directions of pivotal movement of the centralarm and the main arms, the driving magnet undergoes substantially linearalternating movement. Thus the hollow driving coil which is used toelectromagnetically drive the magnet may be disposed very close to thepath of travel of the magnet thereby increasing the driving efficiencyof the vibratory system.

It is therefore a primary object of the present invention to provide animproved vibrator and vibratory system which overcome the drawbacksdescribed above with respect to the prior art systems.

It is another object of the present invention to provide an improvedvibrator and vibratory system utilizing a plurality of vibratory armswhich are dimensioned and arranged in such a manner to sustain vibrationin a normal vibrational mode at a high driving efficiency.

It is still another object of the present invention to provide animproved vibrator and vibratory system employing a pair of mainvibratory arms which are interconnected at both ends to each other andwhich has a pair of central arms extending inwardly towards each othersuch that a driving magnet affixed to one of the central arms undergoesvibration in essentially a linear direction.

Other features and advantages of the vibrator and vibratory systemconstructed in accordance with the principles of the invention will bebetter understood upon a reading of the following specification andappended claims when taken in conjunction with the following drawings,wherein like parts are designated by like reference characters in thevarious views, and wherein:

FIG. I is a plan view of one embodiment of a vibrator constructed inaccordance with the principles of the invention;

FIG. 2 is a plan view of the vibrator shown in FIG. I along withadditional components which make up the vibratory system;

FIG. 3 is a sectional view taken along lines IIIIII in FIG. 2;

FIG. 4 is a right side view of the vibratory system shown in FIG. 2;

FIG. 5 is one embodiment of an electric drive circuit usable with thevibrator of the invention;

FIG. 6 is another embodiment ofan electric drive circuit for use indriving the vibrator of the invention;

FIGS. 7A and 7B are explanatory diagrams depicting the normalvibrational mode of the vibrator;

FIG. 8 is a series ofexplanatory diagrams comparing the normalvibrational mode with the spurious vibra tional modes;

FIG. 9 is a plan view of another embodiment of a vibratory systemaccording to the invention;

FIG. 10 is a sectional view taken along the section line XX in FIG. 9;and

FIG. 11 is a right side view ofthe embodiment shown in FIG. 9.

The vibrator comprises a vibratory unit 1 composed of resilient sheetmaterial having a constant modulus of elasticity. The vibratory unit Ihas a pair ofmain vibratory arms 2,2 which extend in parallel andspacedapart relationship and which are interconnected at one end by aconnecting end portion 3 and at the other end by another connection endportion 4. A pair of central vibratory arms 5 and 6 are connected torespective ones of the connecting end portions 3 and 4 and extendinwardly towards each other as shown in FIG. 1. The dis tal ends ofthese central arms 5 and 6 are spaced-apart from each other to enablethe arms to move independently of each other.

A pair of supporting arms 7 and 8 extend outwardly from the connectingend portion 4 and the supporting arms are connected to a fasteningportion 9. A pair of holes 10,10 are provided in the fastening portion 9and by such a construction, the vibratory unit is fastened to andsupported upon a suitable support member during use of the vibratoryunit.

As shown in FIGS. 24, the vibratory system comprises a support member 13having a bracket portion 12 which is affixed to the vibratory unit I bya pair of screws 1],". The mounting of the vibratory unit I upon thesupport member 13 is such that the unit vibrates about the supportingarms 7 and 8 which comprise fixed nodal points.

A driving magnet 14 is affixed to the free end of the central vibratoryarm by means of a supporting member 15. The driving magnet 14 has acylindrical contig uration and is supported so as to extendperpendicularly with respect to the plane of the vibratory unit 1 andthe longitudinal axis of the driving magnet lies along a center line L.An adjusting screw 16 is threaded into the supporting member and thescrew is selectively threaded into or out of the supporting member toaccordingly regulate the frequency of vibration of the vibrator.

A base plate 19 is disposed beneath the vibrator and spaced-aparttherefrom by means of the supporting member 13. A hollow spool 17 isaffixed to the base plate 19 and the spool has a cylindrical throughborewhich is concentric with the center line L and which is dimensioned toreceive therein the driving magnet 14. The spool l7 is composed ofelectrically insulative material and a pickup-and-driving coil 18 iswound around the spool in such a manner that energization of the coilcreates a magnetic field of sufficient strength to drive the magnet 14in one direction and when the coil is de energized, movement of themagnet 14 past the coil induces a voltage therein in a manner well knownin the art.

A driven magnet 20 is secured to the other side ofthe central arm 5 bymeans of a supporting member 21. As seen in H08. 3 and 4, the drivenmagnet 20 is mounted along the center line L and the magnet 20 has theconfiguration on a yoke having two generally parallel arms which areconnected at one end to the supporting member 21 and which terminate attheir other ends in a pair of arm extensions 22,22. The arm extensionsex tend toward each other and are spaced-apart to define a small gaptherebetween. A magnetic follower wheel 23 is mounted for rotationadjacent the yoke such that the periphery of the follower wheel passesthrough the gap and the arm extensions 22,22 function as magnetic polesand coact with the follower wheel 23 to rotationally drive same in anintermittent manner in response to vibration of the vibratory unit 1.

As seen in FIG. 3, the follower wheel 23 has a plurality ofcircumferentially spaced-apart peripheral teeth 24 and a correspondingplurality of apertures 25 dis posed radially inwardly from the teeth 24.The combi* nation of the teeth 24 and the elongated apertures 25 definea wavy magnetic track on the follower wheel 23 and the track ismagnetically coupled with the mag netic poles 22,22.

A balancing mass 26 is secured to the free end portion of the othercentral arm 6 and the balancing mass is suitably located to insure thatthe center of gravity of the vibrator lies along the center line L andis located in the plane of the vibrator.

One embodiment of an electric drive circuit is shown in FIG. 5 and thedrive circuit comprises an electric power source El having its positiveterminal connected to one side of the pickup-and-driving coil 18 and thenegative terminal of the power source is connected to the emitters oftransistors Trl and Tr2. The other end of the pickup-and-driving coil 18is connected through a resistor R3 to the base ofthe transistor Trl. Thepositive terminal of the power source is also connected to the collectorof the transistor Trl through a resistor R2.

The collector of the transistor Trl is connected to the base of the Tr2through a capacitor C2.

An R-C biasing network comprising a capacitor C1 shunted by a resistorRl is connected between the base and collector ofthe transistor Trl. Aresistor R4 is coupled between the base and the collector of thetransistor Tr2 and this resistor is provided to regulate the frequencyofthe drive circuit. As known in the art, the frequency of the drivecircuit is adjusted to be a little lower than the natural frequency ofthe vibrator l. The circuit functions such that as the vibrator lvibrates, a voltage is induced in the pickup-and-driving coil causingthe transistor Tr2 to turn on thereby delivering driving current to thecoil 18 to drive the driving magnet.

Another embodiment of an electric drive circuit is shown in FIG. 6 andin this embodiment, the single pickup-and-driving coil 18 is separatedinto a driving coil 18a and a pickup coil 1811. An electric power sourceE2 has its positive terminal connected to the emitter of a transistorTr3 and the negative terminal of the power source is connected to thecollector of the transistor Tr3 through the driving coil [80. The baseof the transistor Tr3 is connected to the negative terminal of the powersource E2 through an R-C biasing network composed of a capacitor C3which is shunted by a resistor R5 and the biasing network is in serieswith the pickup coil l8b which in turn is connected to the negativeterminal of the power source. This drive circuit functions in a mannersimilar to that shown in FIG. 5 such that movement of the driving magnetpast the pickup coil 18!) induces a voltage therein which is effectiveto turn on the transistor Tr3 causing current to flow through thedriving coil 18b which in turn drives the magnet back through a returnstroke The mode of operation of the vibratory system will now bedescribed with reference to FIGS. 7A and 78. Referring first to FIG. 7A,as the pair of main vibratory arms 2 and 3 resiliently bend or flexupward, the free end of the vibrator moves leftward a small distance aand at the same time, the central vibratory arm 5 bends upward causingthe free end thereof to move rightward. The leftward movement of thefree end of the vibrator is the result of the small degree of pivotalmovement of the vibrator about the supporting arms 7 and 8 whereas therightward movement of the free end of the central vibratory arm 5 is dueto the small degree of pivotal movement it undergoes about its pivotalpoint which is located at the connecting end portion 3 of the vibrator.It will be appreciated that the two displacements of the free end of thevibrator and the free end of the central arm 5 almost cancel each otherout and therefore the driving magnet 14 and the driven magnet 20 movebasically linearly in an upward direction in one sense along the centerline L. At the same time, the other central vibratory arm 6 flexesdownward in the opposite sense and this condition is shown in FIG. 7Awhich depicts the position of the various elements at the end of onevibratory stroke.

FIG. 7B depicts the position of the same elements at the end of theother vibratory stroke wherein the vibratory arms 2 and 3 areresiliently flexed downward causing the free end of the vibrator 1 tomove leftward a small distance a. At the same time, the centralvibratory arm 5 bends downward and its free end moves rightward almostthe same distance. The two displacements cancel each other out asaforementioned to ef fect substantially linear downward movement of boththe driving magnet 14 and the driven magnet 20 along the center line L.At this time, the other central vibratory arm 6 is flexed upward.

It should be noted that in order to ensure that the relativedisplacements of the free end of the vibrator 1 and the free end of thecentral vibratory arm 5 effectively cancel each other, the dimensions ofthe vibrator itself as well as the dimensions and configurations of thedriving and driven magnets and the balancing mass 26 are designed toeffectuate this purpose. In addition, the adjusting screw 16 iscarefully adjusted to obtain a fine adjustment of the balance of thevibrator thereby ensuring that the driving magnet 14 reciprocates alonga linear axis defined by the center line L. By such a construction, thegap spacing between the coil 18 and the magnet 14 may be reduced to aminimum value since clearance need not be provided to accommodate theangular movement of the driving magnet which has heretofore beennecessary in the prior art devices.

A vibrator and vibratory system actually constructed in accordance withthe principles of the invention has been used and the variousvibrational modes are shown in FIG. 8. The normal vibrational mode A,was l28 Hz and the various vibratory arms vibrated in the manner shown.One spurious vibration mode A had a frequency of 85 Hz and anotherspurious vibration mode 1;, had a frequency of 173 Hz and thevibrational pattern of the vibratory arms was as shown in the drawing.From such an example, it may be readily seen that the frequency of thevibrator when operating in the normal vibration mode A, may be fullysegregated from the frequencies of the spurious vibration modes A and Athereby ensuring that the vibrator vibrates in the normal vibrationalmode. When vibrating in the normal vibrational mode, the quality factorQ of the vibrator was 2,000.

Another embodiment of the vibratory system is shown in FIGS. 9-11 and inthis embodiment, the parts similar to those shown and described withreference to the embodiment of FIGS. 2-4 have corresponding referencenumerals except that they are increased by 100. In this embodiment, thedriven magnet 120 is mounted upon the central vibratory arm 106 by meansof a supporting member 127 and the driving magnet 114 is mounted uponthe central vibratory arm 105. It will be remembered that in the otherembodiment, both the driving and driven magnets were secured to the samecentral arm whereas in this embodiment, the respective magnets aremounted on different ones of the central vibratory arms.

As seen in FIGS. 10 and 11, the supporting member 127 has two brackets128,128 extending in parallel and each connected together at one oftheir end portions to form another supporting member 129. An adjustingscrew 130 is threaded into the supporting member 129 and is used toregulate the balance of the vibrator. In this embodiment, the dimensionsand configurations of the various parts are so constructed such that thecenter of gravity of the moving parts lies along a linear center line asin the former embodiment.

Thus it may be appreciated that according to the present invention, thedriving magnet moves essentially linearly thereby making it possible toreduce the air gap between the driving magnet and the coil to a minimumvalue. Moreover, the normal vibrational mode varies very little even ifthe orientation of the vibrator is varied and this is due to the factthat the center of gravity of the moving parts moves in essentially alinear manner and is not influenced by the attitude ofthe vibrator.Furthermore, since the main vibratory arms 2,2 and one central vibratoryarm bend in opposite directions, the vibrational energy cancels out atthe supporting arms so that very little leakage of the vibrationalenergy occurs at the point of fastening. In addition, the linearmovement of the driving magnet causes a very stable correspondingmovement of the driven magnet and hence the follower wheel is accuratelyrotated.

The vibrator and vibratory system of the invention is especiallysuitable for use as a precision frequency source for a timepiece or thelike and though obvious modifications and changes will become apparentto those skilled in the art, the present invention is intended to coverall such obvious modifications and changes which fall within the spiritand scope of the invention as defined in the appended claims.

What 1 claim is:

1. A mechanical vibrator for a timepiece or the like comprising: avibratory unit composed of resilient sheet material and having two mainvibratory arms disposed in spacedapart generally parallel relationship,two connecting end portions each interconnecting adjacent ends of saidtwo main vibratory arms, and two central vibratory arms connected torespective ones of said connecting end portions and extending inwardlytowards each other, and configured to vibrate, when supported at onesaid connecting end portion and suitably energized, in a normalvibrational mode wherein said two main vibratory arms along with the onecentral vibratory arm which is located remote from said one con nectingend portion all flexurally vibrate in the same sense about theirrespective ends of connection while the other central vibratory armwhich is connected to said one connecting end portion flexurallyvibrates in the opposite sense about its end of connection such that thefree end of said one central vibratory arm undergoes substantial linearvibratory movement; and means including a magnet secured to the free endof said one central vibratory arm for energizing said vibra tory unit inits normal vibrational mode.

2. A mechanical vibrator according to claim 1; wherein said magnet issecured to said free end of said one central vibratory arm at a locationother than midway along the length of said two main vibratory arms.

3. A mechanical vibrator according to claim 1; wherein the center ofgravity of said vibratory unit is situated in the region of said freeend of said one central vibratory arm.

4. A mechanical vibrator according to claim 1; wherein the center ofgravity of said vibratory unit is located in the region of the free endof one of said central vibratory arms.

5. A vibratory system comprising: a mechanical vibrator composed ofresilient sheet material and having two main vibratory arms disposed inspaced-apart generally parallel relationship, two connecting endportions each interconnecting adjacent ends of said two main vibratoryarms, and two central vibratory arms connected to respective ones ofsaid connecting end portions and extending inwardly towards each other;supporting means connected to one of said connecting end portions forsupporting said mechanical vibrator at said one connecting end portionto enable same to vibrate thereabout; a driving magnet secured to a freeend of one of said central vibratory arms; means coacting with saidmechanical vibrator and magnetically coupled with said driving magnetfor magnetically driv ing said magnet to effect vibration of saidmechanical vibrator in a normal vibrational mode wherein said free endof said one central vibratory arm alternately flexes about itscorresponding connecting end portion accompanied by alternate flexing ofsaid two main vibratory arms about said one connecting end portion suchthat said driving magnet alternately moves along a substantially linearpath of travel; a rotatable output member; and means responsive tovibration of said mechanical vibrator for rotationally driving saidoutput member in an intermittent manner.

6. A vibratory system according to claim wherein said mechanicalvibrator is dimensioned and configured to ensure that transversemovement of said driving magnet, relative to its said path of travel,caused by flexing of said one central vibratory arm effectively cancelsout that caused by flexing of said two main vibratory arms so thatdriving magnet undergoes substantially linear alternating movement.

7. A vibratory system according to claim 6; wherein said means formagnetically driving said magnet includes an energizeable coil having ahollow space in the center thereof which is disposed along said path oftravel of said driving magnet and dimensioned to receive therein with aminimum clearance therebetween said driving magnet during linearalternating movement thereof along said path of travel.

8. A vibratory system according to claim 6; wherein said meansresponsive to vibration of said mechanical vibrator includes a drivenmagnet secured to the free end of said one central vibratory arm on theopposite side thereof from said driving magnet and vibrationally drivenby said one central vibratory arm during vibration of said mechanicalvibrator.

9. A vibratory system according to claim 6', wherein said meansresponsive to vibration of said mechanical vibrator includes a drivenmagnet secured to the free end of the other of said central vibratoryarms and vibrationally driven thereby during vibration of saidmechanical vibrator.

1. A mechanical vibrator for a timepiece or the like comprising: avibratory unit composed of resilient sheet material and having two mainvibratory arms disposed in spaced-apart generally parallel relationship,two connecting End portions each interconnecting adjacent ends of saidtwo main vibratory arms, and two central vibratory arms connected torespective ones of said connecting end portions and extending inwardlytowards each other, and configured to vibrate, when supported at onesaid connecting end portion and suitably energized, in a normalvibrational mode wherein said two main vibratory arms along with the onecentral vibratory arm which is located remote from said one connectingend portion all flexurally vibrate in the same sense about theirrespective ends of connection while the other central vibratory armwhich is connected to said one connecting end portion flexurallyvibrates in the opposite sense about its end of connection such that thefree end of said one central vibratory arm undergoes substantial linearvibratory movement; and means including a magnet secured to the free endof said one central vibratory arm for energizing said vibratory unit inits normal vibrational mode.
 2. A mechanical vibrator according to claim1; wherein said magnet is secured to said free end of said one centralvibratory arm at a location other than midway along the length of saidtwo main vibratory arms.
 3. A mechanical vibrator according to claim 1;wherein the center of gravity of said vibratory unit is situated in theregion of said free end of said one central vibratory arm.
 4. Amechanical vibrator according to claim 1; wherein the center of gravityof said vibratory unit is located in the region of the free end of oneof said central vibratory arms.
 5. A vibratory system comprising: amechanical vibrator composed of resilient sheet material and having twomain vibratory arms disposed in spaced-apart generally parallelrelationship, two connecting end portions each interconnecting adjacentends of said two main vibratory arms, and two central vibratory armsconnected to respective ones of said connecting end portions andextending inwardly towards each other; supporting means connected to oneof said connecting end portions for supporting said mechanical vibratorat said one connecting end portion to enable same to vibrate thereabout;a driving magnet secured to a free end of one of said central vibratoryarms; means coacting with said mechanical vibrator and magneticallycoupled with said driving magnet for magnetically driving said magnet toeffect vibration of said mechanical vibrator in a normal vibrationalmode wherein said free end of said one central vibratory arm alternatelyflexes about its corresponding connecting end portion accompanied byalternate flexing of said two main vibratory arms about said oneconnecting end portion such that said driving magnet alternately movesalong a substantially linear path of travel; a rotatable output member;and means responsive to vibration of said mechanical vibrator forrotationally driving said output member in an intermittent manner.
 6. Avibratory system according to claim 5; wherein said mechanical vibratoris dimensioned and configured to ensure that transverse movement of saiddriving magnet, relative to its said path of travel, caused by flexingof said one central vibratory arm effectively cancels out that caused byflexing of said two main vibratory arms so that driving magnet undergoessubstantially linear alternating movement.
 7. A vibratory systemaccording to claim 6; wherein said means for magnetically driving saidmagnet includes an energizeable coil having a hollow space in the centerthereof which is disposed along said path of travel of said drivingmagnet and dimensioned to receive therein with a minimum clearancetherebetween said driving magnet during linear alternating movementthereof along said path of travel.
 8. A vibratory system according toclaim 6; wherein said means responsive to vibration of said mechanicalvibrator includes a driven magnet secured to the free end of said onecentral vibratory arm on the opposite side thereof from said drivingmagnet and vibrationally driven by said one centrAl vibratory arm duringvibration of said mechanical vibrator.
 9. A vibratory system accordingto claim 6; wherein said means responsive to vibration of saidmechanical vibrator includes a driven magnet secured to the free end ofthe other of said central vibratory arms and vibrationally driventhereby during vibration of said mechanical vibrator.